This invention relates generally to a printer, and in particular to an apparatus and a method in an inkjet printer for adjusting the printhead-to-media spacing to accommodate different thicknesses of print media.
In a typical printer, such as an inkjet printer, the default printhead-to-media spacing is typically set to accommodate a commonly used, single-sheet-thickness, bond-weight paper, such as 20-lb. bond-weight paper. Envelopes and other print media are usually substantially thicker than a single sheet of such paper, and because of this, it is desirable to enable printhead-to-media spacing to be adjusted, either via user selection, or via automatic media thickness sensing, or both, so as to accommodate such thicker media.
To accomplish this kind of adjustment in the past, various approaches have been made to effect changes in such spacing. Typically, the carriage which supports the printheads is itself supported on two spaced structures, one of which is called a carriage rod, and the other of which is called an anti-rotation rail. The carriage is mounted for lateral shifting along the carriage rod and also for rocking about the axis of the carriage rod. A portion of the carriage rides back and forth freely on the anti-rotation rail. Rocking of the carriage, which is usually produced by raising and lowering of the carriage where it overlies the anti-rotation rail, is effective to change printhead-to-media spacing. U.S. Pat. No. 6,666,537 discloses an implementation that creates such rocking of a carriage. U.S. Pat. Nos. 5,414,453; 6,616,354; and 6,672,696 disclose other implementations that involve rocking of a carriage to change the printhead-to-media spacing.
For printheads of a small swath, rocking of the carriage about the carriage rod is an acceptable and effective method of adjusting the printhead-to-media spacing. The difference in orifice-and-media spacing for a proximal orifice that defines one end of the swath of a printhead and a distal orifice that defines the other end of the swath is often small and thus negligible.
However, with printheads of larger swaths, such as a one-inch or wider swath, this difference in orifice-and-media spacing for proximal and distal orifices on a printhead may become significant and therefore may no longer be ignored if uniform print quality is to be maintained across all the orifices.